I. Field of the Invention
The present invention relates generally to earth working machines including land levelers, ejectors and scrapers. More particularly, the present invention relates to hopper-equipped, scraper ejectors typical of the type classified in United States Patent Class 37, Subclasses 411, 412, 416, 421, and 431.
II. Description of the Prior Art
In the earth working arts, the well-recognized need for efficient leveling equipment persists. A number of scrapers and ejectors, some of who are equipped with an internal hopper, have evolved. Modern farming operations are streamlined by leveling fields or tracts of land prior to planting or other fieldwork. In fish farming for example, large, uniformly smooth ponds can be excavated and formed by modern ejector-scrapers. Earth removed from the pond center is transported to and dumped upon the pond circumference to form a secure periphery. It is well known that efficiency is enhanced by using scraper machines that can not only dig out earth to be moved, but can temporarily store the material for transportation to the appropriate site for subsequent ejection.
In the prior art, a number of carriage-mounted devices have been proposed to level land. However, in relatively smaller scale operations it is important that high efficiency be achieved. A useable, desirable device would thus combine the operations of cutting or scraping with the operations of transporting and ejecting the earth. A single operator can thus level or dig over certain areas of land, and then transport the dirt for relocation to an adjacent area about the field or pond in a simple repetitive operation. Known ejector-scraper machines typically comprise a wheeled carriage adapted to be towed by a tractor or the like. A large hopper is formed near the center of the apparatus. The hopper is formed between a bottom wall, a portion of the scraper, laterally spaced apart sidewalls, and a rear wall. The hopper receives and temporarily stores earth and debris that enters the hopper through an exposed, front orifice as the machine is drawn across a site by a tractor. A lower, ground-engaging scraper attacks the ground at a predetermined angle that is preferably adjustable. After dirt and debris accumulate and fill the hopper, the hopper must be emptied. Prior to discharge, the user transports the ejector scraper to a portion of the land or field under treatment where a low spot is to be filled, or where an earthen formation is to be established.
Designers of prior ejector-scraper machines have sought to increase the size of the load which could be carried to maximize volumetric efficiency. One of the problems with increasing the capacity of an excavating machine resides in the controlled unloading. Assuming a full hopper of very large capacity, it is readily apparent that such a hopper can be dumped to release the load in one location. It is also apparent that pushing the load out of the hopper at a controlled rate to spread it over an area would require extreme forces. The art has developed to produce a hopper of large capacity, and incorporating an effective means to unload the hopper at a controlled rate.
Discharging the hopper is accomplished either by gravity or more generally by a vertically disposed, dozer-type ejector blade. The blade may be positioned near a rear wall of the hopper, and in some devices, the blade itself forms the rear wall. Typically, the blade is moveable forwardly across the hopper bottom between the sidewalls by hydraulic cylinders. The ram is connected by suitable linkage between the ejector blade and some sturdy fixed point on the scraper chassis. The ram or rams extend at uniform speed and with uniform force to effect full forward travel of the ejector blade. It has been found when moving certain types of earth, such as gumbo and sticky material, it is difficult to prevent the blade from binding as it is deflected angularly. The effect of the ejector plate is often to compact the soil into a tight mass, which becomes firmly stuck to the sides of the hopper. This compaction can cause distortion in the dimensions of the hopper, and irregularities in the displacement of the ejector, all of which decrease efficiency as maintenance chores are increased.
Many types of alignment systems have been proposed for securing the blade. In some designs, guides projecting laterally from the ejector plate are slidably received within suitable slots that are formed in or secured upon the sidewalls. Examples of the foregoing design are seen in U.S. Pat. Nos. 4,308,677, 4,041,625, and 4,133,122. Other designs, such as that seen in U.S. Pat. No. 3,952,432 use guide rollers within the carriage that are interconnected with the ejector blade.
Know prior art designs have attempted to further stabilize the ejector blade with multiple, extendable hydraulic rams. A variety of attachment points between the rams, the carriage and the ejector blade have been employed. The rams apply pressure on different points of the ejector in order to compensate for the varying forces needed to empty the hopper. These multi-ram systems require the use of complex hydraulic flow divider/combiner mechanisms to provide uniform extension and retraction of the rams. Obviously, such mechanisms are more complex and more costly than a single ram system. Still others have adapted a single ram attached to the lower portion of the ejector and stabilizer bars designed to counteract side thrust forces encountered by the ejector as it moves forward to empty the hopper. These mechanisms add to the overall weight of the scrapper, increase the overall number of parts required for operation and owing to the greater complexity, increase the overall cost of operation.
Another problem encountered with prior art earth movers is maintaining a level grade both in removing earth and in transporting the load to a dump site. Machines of this type typically have rear wheels adapted to raise or lower the hopper is response to hydraulic actuators to effect the desired grade level for earth removal. These actuators are also used to elevate the hopper to a higher level to transport the filled hopper to a dump site. These prior art wheel arrangements have a tendency to raise or lower in relation to the desired cutting grade when traveling over uneven terrain. When these machines are raise to the height required for transportation there is a tendency for the wheels to bounce due to the flattening of the tires as they travel over ground irregularities. This bouncing action results in increased stress on the carriage and a decrease in the stability of the machine as it transports the load to a dump site. The previous practice has been to "pre-level" the area with a bulldozer before the final precision work is attempted to avoid the variations in grade. This practice has necessitated the duplication of work involved to effect the desired leveling.
Previous wheel assemblies have attempted to provide a mechanism to allow the chassis to remain stable while the wheels respond to irregularities in the terrain. The range of motion in these previous assemblies is very limited. The wheels are generally connected by a chain or gear mechanism such that the wheels do not operate independently. This limits the variations in terrain that these assemblies are able to accommodate. Thus, such devices are more effective on ground that has been previously leveled. The closest prior art wheel system known to applicant is that of U.S. Pat. No. 5,482,326 that employs a rocker arm pivoted at its midpoint, that supports a pair of spaced apart wheels at its ends.